Risks of Stroke After Coronary Artery Bypass Graft – Recent Insights and Perspectives

Abstract

Stroke is one of the most devastating complications after coronary artery bypass graft (CABG) surgery, entailing permanent disability, a 3–6 fold increased risk of mortality, an incremental hospital resource consumption and a longer length of hospital stay. Notwithstanding advances in surgical, anaesthetic and medical management across the last 10 years, the risk of stroke after CABG has not significantly declined, likely because an older and sicker population is now deemed suitable to undergo CABG. The pathogenesis of stroke is multifactorial, but two variables are believed to play a major role – cerebral embolisation of atheromatous debris arising from the ascending aorta during surgical manipulation and hypoperfusion during surgery. Identification of vulnerable patients at increased risk of stroke before CABG is of paramount importance for the surgical decision-making approach and informed consent. Several models including demographic, clinical and procedural variables have been developed to risk-stratify the hazard of stroke in patients undergoing CABG, but identification of severe atherosclerosis of the ascending aorta and pre-existing cerebrovascular disease are key determinants for appropriate risk stratification and decision-making. Atherosclerotic disease of the ascending aorta can be identified before surgery using transoesophageal echocardiography, computed tomography and magnetic resonance imaging. However, intra-operative ultrasound scanning of the ascending aorta is the diagnostic tool with the best sensitivity and specificity for the detection of atheromatous debris in the ascending aorta. Although many investigators have advocated the use of off-pump CABG to minimise the risk of peri-operative stroke, results from randomised trials and meta-analyses have been inconsistent. Anaortic approaches, including total arterial revascularisation within situgrafting of both mammary arteries, or the use of the HEARTSTRING® seal device avoid any manipulation of the aorta, thus potentially minimising the risk of stroke in high-risk patients. Assessment and treatment of severe carotid artery disease, and aggressive and prompt treatment of post-operative atrial fibrillation are other important strategies that should be routinely implemented to reduce the risk of stroke in patients undergoing CABG.